Photographic dyestuff picture



Patented Aug. 15, 1939 UNITED STATES PATENT OFFICE rnorocaarmc DYESTUFF rrc'ruan No Drawing. Application November 29, 1937, Se-

rial No. 177,058. In Germany December L 8 Claims.

Our present invention relates to subtractive dyestuff pictures.

One of its objects is to provide an improved process of producing subtractive dyestuff pictures in which the dyestuif picture is formed through the intermediary of a silver picture. Further objects of our invention will appear from the detailed specification following hereinafter.

The three-color photographic process is frequently defective in that owing to insumcient adaptation of the colors to one another no pure black is produced or the colors are too harsh and unnatural. Pure dyestuif pictures frequently suffer also from a certain lack of definition. This trouble can be minimized by superimposition of a black-and-white picture and the application of this method is known in four-color printing. An essential disadvantage of this method is that it complicates the process considerably since a fourth component negative must be provided and a fourth printing operation must be performed.

By a modification of the silver dyestufi bleaching-out-process the invention provides the possibility of superimposing a silver picture on each color picture without alteration of the technique of taking and without the provision of further colored photographic layers. One is therefore able, by variation of the operating conditions, to strengthen or soften the silver picture independently of the color picture or to influence its gradation.

The procedure may be as follows:

A diffusely colored silver halide emulsion layer is printed in the usual manner from an original. In the usual silver dyestufi bleaching-out-process the silver halide which still remains afterdevelopment of the silver picture is removed by a fixing bath, the color is bleached at the places at which silver is present by means of a suitable dyestuff bleaching bath and finally the silver is removed. In the process of the invention the photographic material is not fixed after development but at a given moment the development is interrupted in known manner, for example by treatment with dilute acetic acid. The dyestuff bleaching-out-process then follows. If an acid bath is used for the bleaching a treatment with a separate bath for interrupting development can be dispensed with, The silver which has now been developed is then dissolved by means of one of the known oxidizing baths which do not attack the silver halide still present, for example a bichromate and sulfuric acid bath, the remaining silver halide is then illuminated with diffused light and developed 0;" it is blackened without an illumination, for example by treatment with sodium sulfide. In this manner there is produced a silver picture which is superposed on the dyestuff picture. The above described effect produced by this superimposed silver picture is maintained when the silver picture does not consist of metallic silver but of a dark silver salt which is obtained from the silver by chemical reaction, e. g. toning.

The foregoing process may be modified and improved in several respects. For example it is to be recommended that the second illumination should be preceded by a treatment with bisulflte in known manner in order to increase the sensitivity of the silver halide. Since some of the dyestuffs which are useful for the silver dyestuff bleaching-out-process are destroyed by a bichromate-sulfuric acid bath it is frequently advantageous to use for removing the silver an oxidizing agent of milder action; a suitable bath for this purpose is a solution of 100 grams of ironammonium-alum and 100 cc. of concentrated sulfuric acid in 1 liter of water.

In order to avoid fog in the superposed silver picture it is generally advantageous to add to the first developer in known manner a substance which dissolves silver halide, for example ammonia, an alkalisulfocyanide, an organic amine or the like.

In selecting the time of printing and the duration of the development regard must be paid to the dyestuif picture as well as to the silver picture and in particular the silver picture easily becomes too powerful in comparison with the dyestuff picture; it is therefore frequently advantageous to reduce the superposed silver picture by a suitable after-treatment. Thus, for example, a part of the silver halide may be dissolved before the second development by treatment with thiosulfate or with another solvent for silver halide. It is, however, also possible to separate the first development into two stages. In this case the illumination is somewhat more intense and the first development is conducted very cautiously, for example with a dilute developer and for not too long a time, so that in the subsequent bleaching process thequantity of dyestuff which is bleached shall not be too great; then after the bleaching development is continued with a powerful developer which advantageously contains a solvent for silver halide. It will, of course, be understood that the silver picture can also be reduced or intensified subsequently in known manner. In selecting the bleaching bath for proflucing the dyestuif picture care must be taken that the bath does not dissolve the silver halide or atleast not too great an extent; nevertheless bleaching baths which fulfil this condition are ide in a layer containing a dyestufi for the formation of a black-and-white picture. This process requires the printing of a further picture on to the layer and difiers essentially from the process of the present invention in which the undeveloped silver halide is used for the production of the superposed black-and-white picture without a further printing operation. This procedure ofiers considerable advantages. It does not require the production of a fourth component picture for the production of the black-and-white picture and it is not necessary to dry the film in darkness after development and bleaching and then to print a further picture and re-develop. The introduction of a drying operation is itself detrimental to the development, whilst it is difiicult to secure good registration in printing a further picture on to the film which has shrunk during the previous wet treatment. Finally the silver halide in the layer is no longer homogeneous; even if the developed silver is reconverted into silver halide the sensitivity of this regenerated silver halide differs considerably from that of the unchanged silver halide.

The following example illustrates the invention:

A lenticular bi-pack as, for instance, described in U. S. patent specification No. 2,093,655 is printed in known manner on to a silver dyestui! bleaching film having on the one side of the support a blue-green layer and on the other side a purple layer and a yellow layer. The film is developed for 6 minutes with a developer of the following composition:

treated for 12 minutes in a bleaching bath of the following composition:

Hydrochloric acid of- 6 per 0 ent strength 'litnr3 1 l hydroxy 4 methylaminobenzene s 111 fate ams" 80 Potassium bromide do 50 and developed with a developer of the following composition:

Water liters-.. 1 l hydroxy 4 methylaminobenzene s ul fate -grams 6. 5 Hydroquinone do 2 Sodium sulfite sicc do 50 Potassium bromide do 2. 8 Ammonia (d=0.91) cc 1.5

addition to the picture composed of the three dyestuif pictures.

The foregoing process for producing blackand-white pictures superposed on dyestuif pictures is not limited to the silver dyestuf! bleaching-out-process, but is applicable to other subtractive processes in which the dyestuff picture is produced through the intermediary of the silver picture, for example in the color forming development process.

What we claim is:

1. In a process of producing subtractive dyestufi pictures in a photographic material adapted to form a dyestuf! picture by means of the silver dyestuif bleaching-out method, the improvement which comprises superimposing a silver picture on the dyestufi' picture by exposing the photographic material to produce latent silver records therein, developing said material, bleaching the dyestufi at the places at which silver is present without fixing, removing said silver, and transforming the remaining silver halide into the silver picture.

2. In a process of producing subtractive dyestufi pictures in a photographic material adapted to form a dyestuf! picture by means of the silver dyestufi' bleaching-out method, the improvement which comprises superimposing a silver picture on the dyestuif picture by exposing the photographic/material to produce latent silver records therein, developing said material, bleaching the dyestuif at the place at which silver is present without fixing, removing said silver, and transforming the remaining silver halide into the silver picture by diffusely exposing and developing said photographic material.

3. In a process of producing subtractive dyestuff pictures in a photographic material adapted to form a dyestuf! picture by means of the silver dyestufi bleaching-out method, the improvement which comprises superimposing a silver picture on the dyestufi picture by exposing the photographic material to produce latent silver records therein, treating said material with a developer containing a solvent for silver halide. bleaching the dyestufi at the places at which silver is present without fixing, removing said silver, and transforming the remaining silver halide into the silver picture.

4. In a process of producing subtractive dyestufi pictures in a photographic material adapted to form a dyestuff picture by means of the silver dyestufi bleaching-out method, the improvement which comprises superimposing a silver picture on the dyestufi picture by exposing the photographic material to produce latent silver records therein, developing said material, bleaching the dyestuff at the places at which silver is present without fixing, removing said silver and a part of the silver halide remaining after the development by a solvent for silver halide, and transforming the remaining silver halide into the silver picture.

5. In a process of producing subtractive dyestuff pictures in a photographic material adapted to form a dyestufi picture by means of the silver dyestuff bleaching-out method, the improvement which comprises superimposing a silver picture on the dyestufi picture by exposing the photographic material to produce latent silver records therein, developing said material, bleaching the dyestufi at the places at which silver is present without fixing, developing further said photographic material, removing said silver, and trans forming the remaining silver halide into the silver picture.

6. In a process of producing subtractive dyestufi pictures in a photographic material adapted to form a dyestuif picture by means 01' the silver dyestuff bleaching-out method, the improvement which comprises superimposing a silver picture on the dyestuflf picture by exposing the photographic material to produce latent silver records therein, developing said material, bleaching the dyestufi at the places at which silver is present without fixing, removing said silver, transforming the remaining silver halide into the silver picture, and changing the density of said silver picture.

7 In a process of producing subtractive dyestuff pictures in a photographic material adapted to form a dvestufl picture by means of the silver dyestufl bleaching-out method, the improvement which comprises superimposing a silver picture on the dyestufl picture by exposing the photographic material to produce latent silver records therein, developing said material, bleaching the dyestufl at the places at which silver is present without fixing, removing said silver by an acid solution of a ferric salt, and transforming the remaining silver halide into the silver picture.

8. In a process of producing subtractive dyestuil' pictures in a photographic material adapted to form a dyestufi picture by means of the silver dyestufi bleaching-out method, the improvement which comprises superimposing a silver picture on the dyestufi picture by exposing the photographic material to produce latent silver records therein, developing said material, bleaching the dyestufl at the places at which silver is present without fixing, removing said silver, transforming the remaining silver halide into the silver picture, and converting said silver picture into another picture by toning.

GERD HEYMER. WERNER SCHULTZE. 

